Positioning of mobile wireless terminal

ABSTRACT

An apparatus for determining a position of a mobile wireless station comprises means for determining the position of the mobile wireless station in accordance with a position of a first reference wireless station, a position of a second reference wireless station, a first relative angular direction between the mobile wireless station and the first reference wireless station, and a second relative angular direction between the mobile wireless station and the second reference wireless station.

FIELD OF THE INVENTION

[0001] The present invention relates to positioning of a mobile wirelessterminal, and more particularly to determination of the position of amobile wireless terminal carried by a visitor in a place or facilitiesin which the visitor moves about, such as a museum or an amusement park.

BACKGROUND OF THE INVENTION

[0002] It is known that the position of a mobile telephone is determinedby an access point and the determined position is sent to the telephone.In a method used in a mobile telephone system and a PHS (PersonalHandyphone System), the position of a telephone is determined based onthe position of an access point which is closest to the telephone. Theaccuracy or resolution of the positioning is about 100 to 200 m (meters)in the PHS, and is about 800 m or more in the mobile telephone.

[0003] In another method used in the PHS, the position of a mobiletelephone is determined by a plurality of access points in accordancewith respective levels of RF signals received from the telephone. Thepositioning accuracy is about 40 to 70 m.

[0004] It is known that the position of a mobile wireless terminal isdetermined by the triangulation method based on the propagation times ofRF signals from a plurality of access points to the terminal. Thepositioning accuracy is about 10 to 20 m.

[0005] The methods for determining a position in accordance with thelevels or propagation times of an RF signal may be effective in a smallarea where there is no obstacle. In general, however, the radioenvironment changes easily due to, for example, the influence ofmulti-paths caused by a building, a wall or the like. In the methods,therefore, detected values exhibit wide variations depending on a deviceor terminal, and hence the positioning accuracy is low.

[0006] A technique of determining the position of a mobile wirelessterminal by using the GPS (Global Positioning System) is known. In amethod using only the GPS, the positioning accuracy is about 30 to 100m. In another method using the GPS together with an auxiliary system, aposition of a mobile wireless terminal estimated by the GPS is correctedin accordance with information of the position which is measured by areference station. The positioning accuracy is about 5 to 50 m. In thesemethods, the signal processing is complex, and the accuracy may bepossibly lowered at an arbitrary time in accordance with the intentionof the organization managing the GPS satellites. Inside a house or avalley between buildings, the positioning accuracy of the GPS islowered.

[0007] PCT publication WO 95/04943 laid-open by Gernar on Feb. 16, 1995,which claims convention priority of U.S. patent Ser. No. 08/101,945filed on Aug. 4, 1993, discloses a mono-pulse azimuth radar system fortracking an automotive vehicle. In the system, the position of apreceding vehicle is determined in accordance with the distance andangle of the preceding vehicle relative to the own vehicle. In thesystem, however, the position of a mobile terminal is not determined.

[0008] Japanese Patent Publication No. HEI 8-86864 (A) laid-open by Kagoon Apr. 2, 1996 discloses an ETC (Electronic Toll Collection) system inwhich one lane is divided into four areas, received signals from fourantennas of different directionalities are combined with one another todetect the presence or the absence of an incoming vehicle in each of theareas. In this system, in order to perform the detection at highaccuracy in a larger range, many small areas and many antennas for therespective areas are required.

[0009] Japanese Patent Publication No. HEI 6-222124 (A) laid-open byTamaoki et al. on Aug. 12, 1994 discloses a technique in which adirectional antenna is used, and an actual intensity pattern of areceived RF signal transmitted from a mobile unit is matched or comparedwith predetermined intensity patterns of received signals to determinethe position of the mobile unit. The antenna has a relatively largesize, and an apparatus of a large size is necessary for controlling thedirectionality of the antenna.

[0010] It is an object of the invention to determine more correctly theposition of a mobile wireless terminal in a relatively narrow area.

[0011] It is another object of the invention to provide a configuration,which is simpler in structure and smaller in size, for determining theposition of a mobile wireless terminal.

SUMMARY OF THE INVENTION

[0012] In accordance with one aspect of the invention, an apparatus fordetermining a position of a mobile wireless station comprises means fordetermining the position of the mobile wireless station in accordancewith a position of a first reference wireless station, a position of asecond reference wireless station, a first relative angular directionbetween the mobile wireless station and the first reference wirelessstation, and a second relative angular direction between the mobilewireless station and the second reference wireless station.

[0013] In accordance with another aspect of the invention, an apparatusfor determining an angular direction of a wireless station comprisesmeans for determining the angular direction of the wireless stationrelative to a reference angular direction, in accordance with a phasedifference associated with a received RF signal.

[0014] In accordance with a further aspect of the invention, a wirelessapparatus comprises first and second antennas displaced from each otherby a predetermined distance for receiving an RF signal; and means fordetecting a phase difference associated with the received RF signalbetween the first and second antennas.

[0015] In accordance with a still further aspect of the invention, aprogram (which may be stored on a storage medium) is for use in aninformation processing apparatus. The program is operable to effect thestep of obtaining a first relative angular direction between a mobilewireless station and a first reference wireless station; the step ofobtaining a second relative angular direction between the mobilewireless station and a second reference wireless station; and the stepof determining a position of the mobile wireless station. in accordancewith a position of the first reference wireless station, a position ofthe second reference wireless station, the first relative angulardirection, and the second relative angular direction.

[0016] In accordance with a still further aspect of the invention, amethod for determining a position of a mobile wireless station comprisesthe step of obtaining a first relative angular direction between themobile wireless station and a first reference wireless station; the stepof obtaining a second relative angular direction between the mobilewireless station and a second reference wireless station; and the stepof determining a position of the mobile wireless station in accordancewith a position of the first reference wireless station, a position ofthe second reference wireless station, the first relative angulardirection, and the second relative angular direction.

[0017] According to the invention, the position of a mobile wirelessterminal in a relatively narrow area can be determined more correctly,and a configuration, which is simpler in structure and smaller in size,for determining the position of a mobile wireless terminal can beprovided

BRIEF DESCRIPTION OF THE DRAWINGS

[0018]FIG. 1 shows a schematic configuration of a system for determiningthe positions of mobile wireless terminals in a plurality of indoorand/or outdoor areas or facilities, such as a museum or an amusementpark, in accordance with the invention;

[0019]FIG. 2 shows a schematic configuration of another system fordetermining the positions of mobile wireless terminals in the pluralityof indoor and/or outdoor areas, in accordance with the invention;

[0020]FIG. 3 shows a schematic configuration of a communication noderepresenting the reference wireless stations of FIG. 1 having at leastone antenna, and the mobile wireless terminals of FIG. 2 having at leastone antenna;

[0021]FIG. 4 shows a schematic configuration of a communication noderepresenting the mobile wireless terminals of FIG. 1 having at least twoantennas, and the reference wireless stations of FIG. 2 having at leasttwo antennas;

[0022]FIG. 5 shows a flow diagram for determining the position of themobile wireless terminal in accordance with the source ID and the phasedifference between received RF signals;

[0023]FIGS. 6A to 6D show relationships among received data, phasedifferences, frames of angular direction data for determining theposition, and the determined position data of the mobile wirelessterminal;

[0024]FIG. 7A is useful for explaining a method for determining theposition of one mobile wireless terminal in each of the areas in thesystem of FIG. 1, in accordance with the determined angular directionsof the respective three reference nodes relative to the mobile wirelessterminal;

[0025]FIG. 7B is useful for explaining a method for determining theposition of one mobile wireless terminal in each of the areas in thesystem of FIG. 2, in accordance with the determined angular directionsof the terminal relative to the two reference nodes;

[0026]FIG. 8 is useful for explaining a technique of determining theincident angular direction of an RF signal in accordance with the phasedifference of RF signals received by the two antennas of thecommunication node of FIG. 4;

[0027]FIG. 9 shows a block diagram of a process for determining theangular direction of the mobile wireless terminal in accordance with thereceived RF signal;

[0028]FIG. 10 shows a block diagram of another process for determiningthe angular direction of the mobile wireless terminal in accordance withthe received RF signal;

[0029]FIG. 11 shows a block diagram of a further process for determiningthe angular direction of a mobile wireless terminal in accordance withthe received RF signal;

[0030]FIG. 12 shows a block diagram of a logic process for determiningthe direction of a mobile wireless terminal in accordance with thereceived RF signal;

[0031]FIGS. 13A to 13C show logic levels of different signals of FIG. 12for determining the absolute phase difference;

[0032]FIGS. 14A and 14B show logic levels of different signals of FIG.12 for determining the sign of the phase difference;

[0033]FIGS. 15A and 15B are useful for explaining different methods fordetermining the position of the terminal by using a plurality ofreference communication nodes;

[0034]FIG. 16 shows an example of the arrangement of two antennas in themobile wireless terminal in FIG. 1;

[0035]FIGS. 17A and 17B show another example of the arrangement of twoantennas in the mobile wireless terminal in FIG. 1, and an intensitypattern of a received RF signal of this example, respectively; and

[0036]FIG. 18 shows an arrangement which includes a switch forcorrecting an error due to such a path difference.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0037]FIG. 1 shows a schematic configuration of a system for determiningthe positions of mobile wireless terminals or stations 260 and 280carried by the visitors in a plurality of indoor and/or outdoor areas 62and 64 and the like, in a place or facilities, such as a museum or anamusement park, where visitors move about, in accordance with theinvention. A server 110 which provides information to mobile wirelessterminals in the areas and collects information from the terminals, aposition determining apparatus 120 which determines the position of amobile wireless terminal in each area, and an access point 200 which isfixed in position are connected to one another via a wired local areanetwork (LAN) 50. The access point 200 serves also as a referencewireless station which is used as a position reference. The server 110,the position determining apparatus 120, the access point 200 and thelike may be geographically separated from one another, and connected toone another via a public switched telephone network (PSTN), leased linesor the like.

[0038] The server 110 has a processor 112 and a storage device 114. Theprocessor 112 operates in accordance with an application program for theserver function stored in the storage device 114. Alternatively, theserver function may be implemented on the processor 112 in the form ofhardware. The position determining apparatus 120 has a processor 122 anda storage device 124. The processor 122 operates in accordance with anapplication program for the position determining function stored in thestorage device 124. Alternatively, the position determining function maybe implemented on the processor 122 in the form of hardware. Theposition determining apparatus 120 may be eliminated, and the positiondetermining function may be implemented by another apparatus, such asthe server 110, the access point, or another reference wireless stationor mobile wireless terminal as described later.

[0039] The visitors who carry the respective mobile wireless terminals260 and 280 and the like enter the areas 62 and 64 which are indoorand/or outdoor, move in the areas, and then go out of the areas. Thus,the mobile wireless terminals 260 and 280 move around in indoor and/oroutdoor areas including the areas 62 and 64. Each of the mobile wirelessterminals 260 and 280 communicates with the server 110 via the accesspoint 200 to receive suitable guidance information for the currentposition of the terminal from the server 110, and presents theinformation visually or audibly.

[0040] The access point 200, and reference wireless stations 220, 230and 240 cover the areas 62 and 64. The reference wireless stations 220,230 and 240 may communicate in the wireless form with the access point200 to communicate with one another via the access point 200.Alternatively, the reference wireless stations 220, 230 and 240 may beconnected via a cable to the LAN 50. It is assumed that, in the place orthe facilities, the positions A (x₁,y₁), B (X₂,y₂), C (x₃,y₃) and D(X₄,y₄) of the reference wireless stations 200, 220, 230 and 240 areknown. Preferably, the positions of the reference wireless stations 220,230 and 240 are fixed. The reference wireless station may be moved to adifferent position, while the motion of the reference wireless stationdoes not affect the positioning.

[0041] Each of the reference wireless stations 200, 220, 230 and 240 hasat least one antenna for positioning. Each of the mobile wirelessterminals 260 and 280 has at least two antennas for positioning. Thereference wireless stations 200, 220, 230 and 240, and the mobilewireless terminals 260 and 280 serve as communication nodes. Each of thereference wireless stations 200, 220, 230 and 240 transmits an RF signalfor determining the position (x,y) of each of the mobile wirelessterminals 260 and 280. The position (x,y) of each of the mobile wirelessterminals 260 and 280 is determined or detected in accordance with theRF signals received by the mobile wireless terminal as described later.

[0042]FIG. 2 shows a schematic configuration of another system fordetermining the positions of mobile wireless terminals 262 and 282 inthe plurality of indoor and/or outdoor areas 62 and 64 and the like,which is a modification of the system of FIG. 1, in accordance with theinvention. The server 110, the position determining apparatus 120, andan access point 202 which is fixed in position are connected to oneanother via the wired LAN 50. The access point 202 serves also as areference wireless station.

[0043] The mobile wireless terminals 262 and 282 move around in indoorand/or outdoor areas including the areas 62 and 64. Each of the mobilewireless terminals 262 and 282 communicates with the server 110 via theaccess point 202 to receive suitable guidance information for thecurrent position of the terminal from the server 110, and presents theinformation visually or audibly.

[0044] The access point 202, and reference wireless stations 222, 232and 242 cover the areas 62 and 64. The reference wireless stations 222,232 and 242 communicate in the wireless form with the access point 202to communicate with one another via the access point 202. Alternatively,the reference wireless stations 222, 232 and 242 may be connected via acable to the LAN 50. It is assumed that, in the place or the facilities,the positions A, B, C and D of the reference wireless stations 202, 222,232 and 242 are known. Preferably, the positions of the referencewireless stations 222, 232 and 242 are fixed. The reference wirelessstation may be moved to a different position, while the motion of thereference wireless station does not affect the positioning.

[0045] Each of the reference wireless stations 202, 222, 232 and 242 hasat least two antennas for positioning. Each of the mobile wirelessterminals 262 and 282 has at least one antenna for positioning. Thereference wireless stations 202, 222, 232 and 242, and the mobilewireless terminals 262 and 282 serve as communication nodes. Each of themobile wireless terminals 262 and 282 transmits an RF signal fordetermining the position (x,y) of the terminal, to the referencewireless stations 202, 222, 232 and 242. The position (x,y) of theterminal is determined or detected in accordance with the RF signalsreceived by the reference wireless stations 202, 222, 232 and 242, asdescribed later.

[0046]FIG. 3 shows a schematic configuration of a communication node 300representing the reference wireless stations 200, 220, 230 and 240 ofFIG. 1 having at least one antenna, and the mobile wireless terminals262 and 282 of FIG. 2 having at least one antenna. The node 300 has anantenna 351, a frequency converter 353 coupled to the antenna 351, amodem 355 coupled to the frequency converter 353, a signal processor 370coupled to the modem 355, and a memory 372 including a ROM, a RAM andthe like. The memory 372 stores programs and data for the processor 370.

[0047] The signal processor 370 of the access point 200 of FIG. 1 isconnected to the LAN 50. The signal processors 370 of the referencewireless stations 220, 230 and 240 may communicate in the wireless formwith the signal processor 370 of the access point 200 to communicatewith one another via the access point 200. Alternatively, the signalprocessor 370 of each of the reference wireless stations 220, 230 and240 may be connected via a cable to the LAN 50. The signal processor 370of each of the mobile stations 262 and 282 of FIG. 2 communicates in thewireless form with the access point 202.

[0048] The signal processor 370 provides transmitted data and controlsignals for communication to the modem 355, and receives received dataand control signals for communication from the modem. The controlsignals may be transmitted to or received from the server 110 or theposition determining apparatus 120 via the signal processor 370. Thetransmitted data contains a source identifier (ID). A carrier signalmodulated with the transmitted data by the modem 355 is upconverted bythe frequency converter 353 and then transmitted as an RF signal via theantenna 351. On the other hand, an RF signal received by the antenna 351is downconverted to an intermediate frequency (IF) signal by thefrequency converter 353, which is then provided to the modem 355. Thedownconverted signal is demodulated by the modem 355 to produce receiveddata and the received data is provided to the signal processor 370.

[0049]FIG. 4 shows a schematic configuration of a communication node 400representing the mobile wireless terminals 260 and 280 of FIG. 1 havingat least two antennas, and the reference wireless stations 202, 222, 232and 242 of FIG. 2 having at least two antennas. The node 400 has twoantennas 411 and 451, frequency converters 413 and 453 coupled to therespective antennas 411 and 451, respectively, a phase differencedetector 415 coupled to the frequency converters 413 and 453, a modem455 coupled to the frequency converters 413 and 453, an ID detector 457coupled to the modem 455, a signal processor 470, and a memory 472including a ROM, a RAM and the like. The signal processor 470 is coupledto the phase difference detector 415, the modem 455 and the ID detector457. The memory 472 stores programs and data for the processor 470.Alternatively, the ID detector 457 may be eliminated, and the IDdetecting function of the ID detector 457 may be implemented on theprocessor 470.

[0050] The signal processor 470 of each of the mobile stations 260 and280 of FIG. 1 communicates in the wireless form with the access point200. The signal processors 470 of the reference wireless stations 222,232 and 242 of FIG. 2 communicate in the wireless form with the signalprocessor 470 of the access point 202 to communicate with one anothervia the access point 202. Alternatively, the signal processor 470 ofeach of the reference wireless stations 222, 232 and 242 may beconnected via a cable to the LAN 50.

[0051] For positioning, the node 400 of FIG. 4 receives the RF signaltransmitted from the node 300 of FIG. 3, via the antennas 411 and 451.Each of the mobile wireless terminals 260 and 280 of FIG. 1 serving asthe node 400 receives different transmitted RF signals from thereference wireless stations 220, 230 and 240 of FIG. 1 serving as thenode 300. Each of the reference wireless stations 222, 232 and 242 ofFIG. 2 serving as the node 400 receives different transmitted RF signalsfrom the mobile wireless terminals 262 and 282 of FIG. 2 serving as thenode 300.

[0052] Transmitted data, which is produced by the signal processor 470,is provided to the modem 455. A carrier signal modulated with thetransmitted data by the modem 455 is upconverted by the frequencyconverter 413 or 453 and then transmitted as an RF signal to the node300 via the antenna 411 or 451.

[0053] The RF signals from the node 300, which are received via theantennas 411 and 451, are downconverted to IF signals by the respectivefrequency converters 413 and 453. Both of the downconverted signals areprovided to the phase difference detector 415. Alternatively, both ofthe received RF signals, which have not yet been downcoverted in therespective frequency converters 413 and 453, may be provided to thephase difference detector 415. One or both of the downconverted signalsfrom the frequency converters 413 and 453 are provided also to the modem455. When both of the signals are provided to the modem 455, receiveddata on one of the signals are selected by the modem 455, or both thesignals are combined with each other for demodulation in a goodcondition.

[0054]FIG. 5 shows a flow diagram of a process for determining theposition of a mobile wireless terminal in accordance with the source IDdetected by the ID detector 457 and with the phase difference betweenreceived RF signals detected by the phase difference detector 415 of thenode 400. The position is determined by the processor 122, 112, 470 or370 of the position determining apparatus 120, the server 110, the node400 or the node 300, in accordance with a program stored in thecorresponding storage device 124, 114, 472 or 372.

[0055] At Step 501 of FIG. 5, the processor 122, 112, 470 or 370 obtainsthe source ID and the phase difference between received RF signals. AtStep 503, the processor derives, from the source ID and the phasedifference, a relative angular direction between the mobile wirelessterminal and the reference node. At Step 505, the processor determinesthe position of the mobile wireless terminal in accordance with theknown position of the reference node, the source ID, and the relativeangular direction.

[0056]FIGS. 6A to 6D show relationships among received data DATA₁, DATA₂and DATA₃ demodulated by the modem 455, phase differences (PDs), Aφ₁,Aφ₂ and Aφ₃, detected by the phase difference detector 415, frames ofangular direction data for determining the position, and the determinedposition data (x,y) of a mobile wireless terminal ID_(T1).

[0057] Referring also to FIG. 4, the received data DATA₁, DATA₂ andDATA₃ of FIG. 6A which are produced by the modem 455 are provided to thesignal processor 470. The received data from each node 300 contains thesource ID of the node 300. The received data DATA₁, DATA₂ and DATA₃contain respective source IDs, ID₁, ID₂ and ID₃, of the referencewireless stations 200, 220, 230 and 240 of FIG. 1, or the mobilewireless terminals 262 and 282 and the like of FIG. 2. The received setsof data, DATA₁, DATA₂ and DATA₃, are provided also to the ID detector457. The ID detector 457 detects and extracts the source IDs, ID₁, ID₂and ID₃, in the received data to provide the extracted IDs to the signalprocessor 470. The phase differences PDs, Aφ₁, Aφ₂ and Aφ3, of FIG. 6Bdetected by the phase difference detector 415, as described later, areprovided to the signal processor 470.

[0058] The signal processor 470 of the communication node 400 determinesthe angular directions of the mobile wireless terminals 260 and 280 inaccordance with the phase differences PDs, combines the determinedangular directions with the source IDs to send the determined angulardirections combined with the source IDs to another node or apparatus.The calculation of the angular direction in accordance with the phasedifference may be performed by the phase difference detector 415, in themanner described later. As shown in FIG. 6D, the position (x, y) of themobile wireless terminal (I_(DT1)) is determined in accordance with theframes of the sets of the source ID and the angular direction shown inFIG. 6C, in the manner described later. The sets of the source ID andthe angular direction, (ID₁, θ₁), (ID₂, θ₂) and (ID₃, θ₃), are sent toanother apparatus, preferably, the position determining apparatus 120 inorder to determine the position of the mobile wireless terminal shown inFIG. 6D. The determined position may be sent to the mobile wirelessterminal for use in the terminal. Alternatively, in the mobile wirelessterminal 260 or 280 of FIG. 1, the position of the terminal may bedetermined by the own signal processor 470 without sending the angulardirection sets to another apparatus.

[0059] As described above, the signal processor 470 of the node 400 maysend the frames of the source ID and the angular direction shown in FIG.6C, to the other node, and the position shown in FIG. 6D may bedetermined by the other node or apparatus. For example, the signalprocessor 470 may send the frames to the position determining apparatus120 via the access point 200 or 202 and the LAN 50, and the positiondetermining apparatus 120 may determine the position in accordance withthe frames. For example, the signal processor 470 may send the frames tothe server 110 via the access point 200 or 202 and the LAN 50, and theserver 110 may determine the position in accordance with the receivedframes. For example, the signal processor 470 may send the frames to theone communication node 300, and the signal processor 370 of thecommunication node 300 may determine the position in accordance with thereceived frames. For example, the signal processor 370 or 470 of theaccess point 200 or 202 may collect the frames from the other nodes anddetermine the position in accordance with the received frames. When theposition determination is performed by an apparatus other than themobile wireless terminals 240, 260, 242 and 262, the processing load inthe terminals can be reduced.

[0060] Alternatively, the signal processor 470 of the node 400 mayproduce frames (not shown) including respective sets of the source IDand the phase difference PD, (ID₁, θ₁), (ID₂, θ₂) and (ID₃, θ₃), andsend the frames to another node. The angular direction and the positionare determined by the other node or apparatus in accordance with thesource ID and the phase difference PD.

[0061] The communication between the reference wireless station and themobile wireless terminal, and hence communication units of the nodes 300and 400 operate in accordance with, typically, a short distance wirelesscommunication standard such as the Bluetooth standard or a wireless LANstandard. The Bluetooth standard uses the 2.4 GHz band (2.402 GHz-2.480GHz) called ISM (Industrial, Scientific and Medial) band. It definesthree power classes 1 to 3 for 1 mW, 2.5 mW and 100 mW. In Power Classes1 to 3, short distance communications in a range of about 10 m to about100 m can be done. The Bluetooth employs the GFSK modulation and thefrequency hopping scheme. The wireless LAN standard, such as IEEE802.11, uses the 2.4 GHz band (2.40 GHz-2.497 GHz) and employs thespread spectrum scheme and the DBPSK or DQPSK modulation, or thefrequency hopping scheme and the GFSK modulation, for communications.

[0062]FIG. 7A is useful for explaining a method for determining theposition (x,y) of one mobile wireless terminal T in each of the areas inthe system of FIG. 1, in accordance with the determined angulardirections θ₁, θ₂ and θ₃ of the respective three reference nodes orreference wireless stations A, B and C relative to the mobile wirelessterminal T. For that purpose, it is assumed that the positions of thethree reference nodes A, B and C are known.

[0063] In FIG. 7A, it is assumed that the mobile wireless terminal T hasa reference angular direction, i.e. reference direction of the angle, orazimuth RT which is determined as described later. The determinedangular directions between the reference direction RT in the mobilewireless terminal T and the three reference nodes A, B and C areindicated by θ₁, θ₂ and θ₃, respectively. The three referencecommunication nodes A, B and C are three ones of the reference wirelessstations 200 to 240 of FIG. 1. When the three reference nodes A, B and Care placed so that a straight line connecting the positions of thereference nodes A and B, and a straight line connecting the positions ofthe reference nodes B and C lie outside the area, the position of themobile wireless terminal T can be uniquely determined in accordance withthe determined angular directions θ₁, θ₂ and θ₃ because the positions ofthe reference nodes A, B and C are known.

[0064] When the reference angular direction RT is adapted by any meansto constantly indicate geographically the same azimuth and the tworeference nodes A and B are placed so that the straight line connectingthe positions of the two reference nodes A and B lies outside the area,the position of the mobile wireless terminal T can be uniquelydetermined in accordance with the angular directions of the tworeference nodes relative to the reference direction RT in the mobilewireless terminal T, for example, the angular directions θ₁ and θ₂ ofthe nodes A and B.

[0065]FIG. 7B is useful for explaining a method for determining theposition (x,y) of one mobile wireless terminal T in each of the areas inthe system of FIG. 2, in accordance with the determined angulardirections θ₁ and θ₂ of the mobile wireless terminal T relative to thetwo reference nodes A and B in the system. The position of the mobilewireless terminal T is determined in accordance with at least twodetermined angular directions of the mobile wireless terminal T. It isassumed that the positions of the two reference nodes A and B are known.

[0066] In FIG. 7B, it is assumed that the two reference communicationnodes A and B have reference angular directions R_(A) and R_(B),respectively. It is assumed that the determined angular directionsbetween the mobile wireless terminal T and the reference directionsR_(A) and R_(B) in the two reference communication nodes A and B areindicated by θ₁ and θ₂, respectively. The two reference communicationnodes A and B are two ones of the reference wireless stations 202 to 242of FIG. 2.

[0067] When the reference angular directions R_(A) and R_(B) of the tworeference communication nodes A and B are determined independently ofeach other, an angular direction θ₁₂ between the reference directionR_(A) in the one reference communication node A and the other node B,and an angular direction θ₂₁ between the reference direction R_(B) inthe other reference communication node B and the one node A aredetermined, and the position of the mobile wireless terminal T can beuniquely determined in accordance with the known positions of the tworeference communication nodes A and B, and with the determined angulardirections, θ₁₂, θ₂₁, θ₁ and θ₂, i.e. (θ₁₂-θ₁) and (θ₂₁-θ₂). In order todetermine the angular directions θ₁₂ and θ₂₁, each of the referencecommunication nodes A and B in the form of the node 400 of FIG. 4receives an RF signal which contains the source ID, which is transmittedfrom the other reference communication node (400) B or A via the antenna411 or 451 of the one node, and which is similar to the RF signal fromthe node 300 of FIG. 3.

[0068] On the other hand, when the relationship between the referenceangular directions or azimuths R_(A) and R_(B) in the positions of thetwo reference communication nodes A and B is known and the referencenodes A and B are placed so that the straight line connecting thepositions of the two reference nodes A and B lies outside the area, theposition of the mobile wireless terminal T can be uniquely determined inaccordance with the known positions of the two reference communicationnodes A and B and with the determined angular directions θ₁ and θ₂relative to the reference directions R_(A) and R_(B).

[0069]FIG. 8 is useful for explaining a technique of determining theincident angular direction of an RF signal in accordance with the phasedifference of RF signals received by the two antennas ANT1 (411) andANT2 (451) of the communication node 400 of FIG. 4, or of IF signals onthe RF signals. An RF signal at, for example, a frequency in thevicinity of 2.5 GHz has a wavelength X of about 12 cm. The antennas ANT1and ANT2 are on a horizontal line and displaced from each other by adistance d (<λ/2) of, for example, about 3 cm. A straight line passingthe positions of the antennas ANT1 and ANT2 is defined as the antennareference line. A direction on a horizontal plane perpendicular to theantenna reference line is defined as a reference angular direction R ofthe communication node 400. It is advantageous to use the referencedirection R as the reference directions R_(T), R_(A) and R_(B) in FIGS.7A and 7B.

[0070] Referring to FIG. 8, when an RF signal, which horizontally entersat an angle θ relative to the reference direction R, is received by theantennas ANT1 and ANT2, the path difference is d·sin θ. The phasedifference between the two antennas ANT1 and ANT2 is Δφ=2π(d·sinθ)/λ.Therefore, the incident angular direction of the RF signal relative tothe reference direction R is θ=Sin⁻¹((λ/2π)Δφ).

[0071] When the reference angular direction R_(T) of the mobile wirelessterminal T, as described in connection with FIG. 7A, is adapted toconstantly indicate geographically the same azimuth, for example, thedirection of the N-pole, the determined values of the angular directionscan be corrected by the difference of the reference angular direction Rof FIG. 8 relative to the reference angular direction R_(T) which isdetermined by using a gyroscope, a compass or the like that can beprovided in the mobile wireless terminal T.

[0072]FIG. 9 shows a block diagram of a process for determining theangular direction θ of the mobile wireless terminal in accordance withthe received RF signal. FIG. 9 can be seen as a flowchart of the processfor determining the direction. An RF signal, which is received by theantenna ANT1 411, is downconverted by the frequency converter 413 toproduce an IF signal A₁cos(ω+φ₁), where A₁ indicates the amplitude, ωindicates the angular velocity, and φ₁ indicates the initial angularphase. An RF signal, which is received by the antenna ANT2 451, isdownconverted by the frequency converter 453 to produce an IF signalA₂cos(ωt+φ₂), where A₂ indicates the amplitude, ω indicates the angularvelocity, and φ₂ indicates the initial angular phase. The IF signalshave a frequency of, for example, 50 MHz. Alternatively, as describedabove, the signals A₁cos((ωt+φ₁) and A₂cos((ωt+φ₂) may be RF signalswhich have not yet been downcoverted. The signals A₁cos(ωt+φ₁) andA₂cos(ωt+φ₂) are provided to the phase difference detector 415.

[0073] In the phase difference detector 415, the signals A₁cos(ωt+φ₁)and A₂cos(ωt+φ₂) are corrected in amplitude by amplitude correctors 417and 457, each of which is configured by a limiting amplifier, to benormalized, to thereby produce normalized signals cos (ωt+φ₁) and cos(ωt+φ₂)

[0074] Both of the normalized signals cos(ωt+φ₁) and cos(ωt+φ₂) areprovided to an adder 419 and to a subtracter 459. The adder 419 producesa sum of the signals, cos(ωt+φ₁)+cos((ωt+φ₂)=cos(ω₁−φ₂)/2)cos(ωt+(φ₁+φ₂)/2). The subtracter 459 produces a signal representing thedifference between the signals,cos(ωt+φ₁)−cos(ωt+φ₂)=−sin((ωt+φ₂)/2)sin(ωt+φ₁+φ₂)/2).

[0075] The sum and difference signals are squared by square-lawdetectors 422 and 462, respectively, and the level or magnitude of asquare of the sum, cos²((φ₁−φ₂)/2), and that of a square of thedifference, sin²((φ₁−φ₂)/2), are determined in respective leveldetectors 424 and 464. The levels are provided to a divider 426. In thedivider 426, sin² ((φ₁−φ₂)/2)/cos²((φ₁−φ₂)/2) tan²((φ₁−φ₂)/2) isdetermined in accordance with the levels to produce a square root of thevalue, |tan((φ₁−φ₂)/2)|=tan(|φ₁−φ₂|/2), and produce the absolute valueof the phase difference |Aφ|=|φ₁−φ₂|. The absolute value of the phasedifference |Δφ| is provided to an incident direction determining device480. Preferably, each of the level detectors 424 and 464 includes an A/Dconverter and provides a digital signal as an output.

[0076] On the other hand, the sum signal is provided also to anamplitude corrector 434 configured by a limiting amplifier, to becorrected in amplitude and normalized, to thereby produce a signalcos(ωt+(φ₁+φ₂)/2)). The difference signal is delayed by π/2 in a delayelement 432 to produce a signal sin((φ₁−φ₂)/2)cos(ωt+(φ₁+φ₂)/2). Thedelayed signal is provided to an amplitude corrector 435 configured by alimiting amplifier, to be corrected in amplitude and normalized, tothereby produce a signal sgn(+1−φ₂)·cos(ωt+(φ₁+φ₂)/2), where sgn(x)=+1for x>0, and sgn(x)=1 for x<0.

[0077] The signal cos(ωt+(φ₁+φ₂)/2) from the amplitude corrector 434 isadded to the signal sgn (φ₁−φ₂)·cos(ωt+(φ₁+φ₂)/2) from the amplitudecorrector 435 in an adder 442. The adder 442 produces a value of two (2)for the phase difference φ₁−φ2>0 (zero), i.e. positive, and the adderproduces a value of zero (0) for the phase difference φ₁−φ₂<0 (zero),i.e. negative. The output of the adder 442 is thresholded by a signdetermining device 444 to determine the value as either positive (+) ornegative (−). The positive/negative sign is provided as the sign of thephase difference (φ₁−φ₂) to the incident direction determining device480.

[0078] In the manner described in connection with FIG. 8, the incidentdirection determining device 480 determines the incident angulardirection θ of the RF signal in accordance with the absolute phasedifference |Δφ|=|φ₁−φ₂|, the sign (+ or −) of the phase difference, andthe distance d between the antennas.

[0079] Alternatively, the function for determining the incident angulardirection in the incident direction determining device 480, or fordetermining the incident angular direction in the divider 426 and theincident direction determining device 480 may be performed by the signalprocessor 470 of the node 400, another node, another apparatus or thelike rather than the phase difference detector 415. When the function isperformed in another node or apparatus, the level signals which areprovided from the level detectors 424 and 464 in FIG. 9 to the divider426, and the sign signal which is provided from the sign judgementdevice 444 to the incident direction determining device 480 may be sentin combination with the source ID to the other node or apparatus, and,for example, to the position determining apparatus 120 via the accesspoint 200 or 202 and the LAN 50.

[0080]FIG. 10 shows a block diagram of another process for determiningthe angular direction θ of the mobile wireless terminal in accordancewith the received RF signal, which is a modification of the process ofthe block diagram of FIG. 9. FIG. 10 also can be seen as a flowchart ofthe process for determining the direction. In the process of FIG. 10, inplace of the divider 426 and the incident direction determining device480 of FIG. 9, a ROM table 482 for determining the incident direction,or a processor 482 including such a ROM table is provided. The ROM table482 uses, as indices, both of the levels of a square of the sum,cos²(φ₁−φ₂)/2), and a square of the difference, sin²((φ₁−φ₂)/2), fromthe respective level detectors 424 and 464, and the sign from the signdetermining device 444, to provide, as an output, the value of thecorresponding incident angle θ of the RF signal. In the ROM table 482, atable is provided which correlates the indices with the value of theincident direction θ in accordance with the equations which have beendescribed in connection with FIG. 8.

[0081]FIG. 11 shows a block diagram of a further process for determiningthe angular direction 0 of a mobile wireless terminal in accordance withthe received RF signal, which is a modification of the process of theblock diagram of FIG. 10. FIG. 11 also can be seen as a flowchart of theprocess for determining the direction. In the process of FIG. 11, inplace of the square-law detectors 422 and 462 and the level detectors424 and 464 of FIG. 10, a square-law detector 423 and a level detector425 are connected between switches 420 and 430. The switch 420 isswitched in synchronization by a switching control signal to alternatelyprovide the sum cos((φ₁−φ₂)/2)cos(ωt+(φ₁−φ₂)/2) from the adder 419 andthe difference −sin((φ₁−φ₂)/2)sin(ωt+(φ₁−φ₂)/2) from the subtracter 459to the square-law detector 423 and the level detector 425. The switch430 alternately provides the level of a square of the sum,cos²((φ₁−φ₂)/2), and the level of a square of the difference,sin²((φ₁−φ₂)/2), to the ROM table 482. In the same manner as the tabledescribed above, the ROM table 482 provides, as an output, the value ofthe corresponding incident angular direction θ of the RF signal.

[0082] In FIGS. 10 and 11, alternatively, the ROM table 482 may beprovided in the signal processor 470 of the node 400, another node,another apparatus or the like rather than the phase difference detector415, to determine the incident angular direction. When the incidentangular direction is determined in another node or apparatus, the levelsignals provided from the level detectors 424 and 464 or from the leveldetector 425 via the switch 430 to the ROM table 482, and the signsignal provided from the sign determining device 444 to the ROM table482 may be sent in combination with the source ID to the other node orapparatus, and, for example, to the position determining apparatus 120via the access point 200 or 202 and the LAN 50.

[0083]FIG. 12 shows a block diagram of a logic process for determiningthe direction of a mobile wireless terminal in accordance with thereceived RF signal, as an alternative to the processes of FIGS. 9 to 11.FIG. 12 also can be seen as a flowchart of the process for determiningthe direction.

[0084]FIGS. 13A to 13C show logic levels of different signals of FIG. 12for determining the absolute phase difference. FIGS. 14A and 14B showlogic levels of different signals of FIG. 12 for determining the sign ofthe phase difference.

[0085] Referring to FIG. 12, the signal from the frequency converter 413of FIG. 4 is provided to a binarizing element 467, and thresholded inthe binarizing element 467 to produce a binary signal A. The signaloutput from the frequency converter 453 of FIG. 4 is provided to abinarizing element 477, and thresholded in the binarizing element 477 toproduce a binary signal B.

[0086] The signal A from the binarizing element 467 is provided to oneinput of an exclusive OR (EXOR) gate 469, and the signal B of thebinarizing element 477 is provided to the other input of the exclusiveOR (EXOR) gate 469. The EXOR gate 469 EXORs the signal A with the signalB to provide an EXOR output. FIGS. 13A and 13B show relationships amongsignals when the signal A is advanced in phase from the signal B. FIG.13C shows relationships among signals when the signal A is delayed inphase from the signal B. As shown in FIGS. 13A to 13C, as the absolutephase difference |Δφ| between the signals A and B becomes larger, thepulse width of the EXOR output becomes larger. The pulse width of theEXOR output indicates the absolute phase difference.

[0087] The output from the EXOR gate 469 is provided to a low-passfilter (LPF) 472, and filtered by the LPF 472 to convert the phasedifference into an analog level. The analog level of the analog signaloutput from the LPF 472 is detected as a digital value by a leveldetector 474 to produce the absolute phase difference |Δφ|=|φ₁−φ₂|. Theabsolute phase difference |Δφ| is provided to an incident directiondetermining device 486.

[0088] Referring to FIG. 12, the signal B from the binarizing element477 is provided also to a latch element 437. In the latch element 437,the signal B is latched at a rising edge of the signal A of thebinarizing element 467.

[0089] As shown in FIG. 14A, when the signal A is advanced in phase fromthe signal B, an output of the latch element 437 is always at the Low(L) level. As shown in FIG. 14B, when the signal A is delayed in phasefrom the signal B, the output from the latch element 437 is always atthe High (H) level. The signal, indicating the H or L level, from thelatch element 437 is provided to a sign determining device 445. When thesignal is at the H level, the sign determining device 445 provides thesign of positive (+) to the incident direction determining device 486,and, when the signal is at the L level, the sign determining deviceprovides the sign of negative (−) to the incident direction determiningdevice 486.

[0090] In the manner described in connection with FIG. 8, the incidentdirection determining device 486 determines the incident angulardirection θ of the RF signal in accordance with the absolute phasedifference |Δφ|=|φ₁−φ₂|, the sign (+ or −) of the phase difference, andthe distance d between the antennas. The incident direction determiningdevice 486 may include a ROM table, which is similar to that shown inFIG. 10, and in which the absolute phase difference and the sign areused as indices.

[0091] Alternatively, the function for determining the incident angulardirection in the incident direction determining device 486 may beperformed by the signal processor 470 of the node 400, another node,another apparatus or the like rather than the phase difference detector415. When the function is performed in another node or apparatus, thelevel signal provided from the level detector 474 in FIG. 12 to theincident direction determining device 486, and the sign signal providedfrom the sign judgement device 445 to the incident direction determiningdevice 486 may be sent in combination with the source ID to the othernode or apparatus, and, for example, the position determining apparatus120 via the access point 200 or 202 and the LAN 50.

[0092]FIGS. 15A and 15B are useful for explaining different methods fordetermining the position of a terminal by using a plurality of referencecommunication nodes. In FIGS. 15A and 15B, it is assumed that adetermined angle between an angular direction D_(A) of the terminal Trelative to the reference node A and an angular direction D_(B) of theterminal T relative to the reference node B is θ_(AB), a determinedangle between the angular direction D_(B) of the terminal T relative tothe reference node B and an angular direction D_(C) of the terminal Trelative to the reference node C is θ_(BC), and an determined anglebetween the angular direction D_(C) of the terminal T relative to thereference node C and the angular direction D_(A) of the terminal Trelative to the reference node A is θ_(CA).

[0093] The position determining apparatus 120 of FIGS. 1 and 2, theserver 110 of FIGS. 1 and 2, the signal processor 470 of the node 400 ofFIG. 4, or the signal processor 370 of the node 300 of FIG. 3 obtainsthe sets of the source ID and the angular direction, (ID₁,θ₁), (ID₂,θ₂)and (ID₃,θ₃), to determine the position (x,y) of the terminal T asdescribed above.

[0094] From FIG. 7A, it is seen that, when the system of FIG. 1determines the position of a mobile wireless terminal by using more thanthree reference wireless stations, different terminal positions may beobtained for different combinations of the reference wireless stationsdue to measurement errors of angular directions. From FIG. 7B, it willbe seen that, when the system of FIG. 2 determines the position of amobile wireless terminal by using more than two reference wirelessstations, different terminal positions may be obtained for differentcombinations of the reference wireless stations due to a measurementerror of angular directions.

[0095] Referring to FIG. 15A, when a provisional position of theterminal T which is determined in accordance with the angular directionD_(A) of the terminal T relative to the reference node A and the angulardirection D_(B) of the terminal T relative to the reference node B, witha provisional position of the terminal T determined in accordance withthe angular direction D_(B) Of the terminal T relative to the referencenode B and the angular direction D_(C) of the terminal T relative to thereference node C, and with a provisional position of the terminal Tdetermined in accordance with the angular direction D_(C) of theterminal T relative to the reference node C and the angular directionD_(A) of the terminal T relative to the reference node A do not coincidewith each other, the position determining apparatus 120, the server 110,or the signal processor 470 or 370 determines the average of thedetermined provisional positions in an orthogonal coordinate system(x,y) as an appropriate position of the terminal T. Alternatively, thecenter of gravity of a polygon in which the vertexes lie respectively onthe provisional positions may be determined as an appropriate positionof the terminal T.

[0096] Referring to FIG. 15B, when a provisional position of theterminal T determined in accordance with the angular direction D_(A) andthe angular direction D_(B), a provisional position of the terminal Tdetermined in accordance with the angular direction D_(B) and theangular direction D_(C), and a provisional position of the terminal Tdetermined in accordance with the angular direction D_(C) and theangular direction D_(A) do not coincide with each other, a provisionalposition which has an angle closest to a right angle (90°) among thedetermined angles θ_(AB), θ_(BC) and θ_(CA) is determined or selected asan appropriate position of the terminal T. Alternatively, several angleswhich are closest to a right angle are extracted from the angles θ_(AB),θ_(BC) and θ_(CA), and the average of the provisional positions havingthe extracted angles may be determined as an appropriate position of theterminal T. Alternatively, angles which are in a range of 45 to 135degrees are extracted from the angles, and the average of theprovisional positions with the extracted angles may be determined as anappropriate position of the terminal T.

[0097]FIG. 16 shows an example of the arrangement of two antennas a₁ anda₂ in each of the mobile wireless terminals 260 and 280 in FIG. 1.Referring to FIG. 16, the antennas a₁ and a₂ are placed on or near theupper surface of the mobile wireless terminal 260 or 280 and displacedfrom each other by a distance d. Preferably, each of the antennas a₁ anda₂ is a chip or planar antenna having one side edge of about 1 cm orless. The intensity pattern of the received and transmitted RF signalsfor the antennas a₁ and a₂ is substantially uniform in all of thehorizontal directions, and the antennas a₁ and a₂ can receive an RFsignal radiated from an antenna of a reference node in an arbitrarydirection. Preferably, the antennas a₁ and a₂ are placed inside theterminal, and are not required to be exposed to the outside.

[0098]FIGS. 17A and 17B show another example of the arrangement of twoantennas in the mobile wireless terminal 260 or 280 in FIG. 1, and anintensity pattern of the received RF signal of this example,respectively. Referring to FIG. 17A, a pair of antennas a₁₁ and a₁₂ areplaced on or near the front surface of the mobile wireless terminal 260or 280 and displaced from each other by a distance d. Another pair ofantennas a₂₁ and a₂₂ are placed on or near the back surface of themobile wireless terminal 260 or 280 and displaced from each other by thedistance d. Preferably, each of the antennas a₁₁, a₁₂, a₂₁ and a₂₂ is achip or planar antenna having one side edge of about 1 cm or less. Thepair of antennas a₁₁ and a₁₂ exhibit higher directionality in a half ofthe air space outside the terminal in front of the associated surface,and the received and transmitted RF signal intensity pattern exhibitshigher intensity in the half of the air space. The other pair ofantennas a₂₁ and a₂₂ exhibit higher directionality in another half ofthe air space outside the terminal in back of the opposite associatedback surface, and the received and transmitted RF signal intensitypattern exhibits higher intensity in the other half of the air space.Preferably, the antennas a₁₁ and a₁₂ and the antennas a₂₁ and a₂₂ areplaced inside the terminal, and are not required to be exposed to theoutside. Since the two pairs of antennas of high directionality aredisposed as described above, the mobile wireless terminal 260 or 280 canreceive an RF signal radiated from an antenna of a reference node in anarbitrary direction, and can determine whether the incident directioncorresponds to the front side direction or the back side direction ofthe terminal, without considering the area arrangement.

[0099] The reference wireless stations 202, 222 and 242 of FIG. 2 mayhave the same antenna arrangement as shown in FIG. 16 or 17. Thereference wireless stations 202, 222 and 242 may have a pair of antennasof high directionality which are directed to the positioning areas 62and 64, to thereby reduce the influence of multi-paths. When the size ofthe apparatus can be made larger, the reference wireless stations 202,222 and 242 may have two parallel rod antennas.

[0100] In the above description, it is assumed that the mobile wirelessterminals 260 to 282 and the reference wireless stations 200 to 242 aresubstantially on the same horizontal plane, and the vertical heightdifference between the antennas, and the inclinations of the antennareference lines of the terminals relative to the horizontal plane arenegligible or in the range of a tolerable error. The distances betweenthe reference wireless stations 200 to 242 are, for example, about 5 to10 m. The antennas of the reference wireless stations 200 to 242 have aheight in the range of, for example, about 1.5 to 2 m. The antennas ofthe mobile wireless terminals 260 to 282 have a height in the range of,for example, about 1 to 1.5 m. In this case, the accuracy or resolutionof the positioning of the terminal is expected to be within about 1 m.

[0101] However, when the height difference between the antennas, and theinclinations of the antenna reference lines are negligible, thedirection and the position are three-dimensionally corrected inaccordance with the known heights of the antennas of the referencewireless stations 200 to 242 and the known geography or contour of theareas, to thereby determine the position of each of the mobile wirelessterminals 260 to 282.

[0102] When RF signals received by the two antennas a₁ and a₂ areprocessed by the communication node 400 of FIG. 4, the phase differenceΔφ may exhibit an error e due to the difference of the circuits of thepaths in the communication node 400. FIG. 18 shows an arrangement whichincludes a switch SW for switching connections between two antennas andtwo paths for correcting an error due to such a path difference.

[0103] First, the switch SW is placed on a first pole to provide an RFsignal received via the antenna a₁ to a path 1 including the frequencyconverter 413 in FIG. 4, and provide an RF signal received via theantenna a₂ to a path 2 including the frequency converter 453. It isassumed that an output from the phase difference detector 415 exhibits aphase error e. Thus, the detected phase difference is Δφ+e. The switchSW is then placed on a second pole to provide an RF signal received viathe antenna a₁ to the path 2 including the frequency converter 453, andprovide an RF signal received via the antenna a₂ to the path 1 includingthe frequency converter 413. The detected phase difference is Δφ−e. Inorder to correct the error e, the subtraction is performed on the twophase differences to cancel the error e to obtain the result 2Δφ. Theresult is divided by two (2) to produce a corrected phase difference Δφ.

[0104] The above-described embodiments are only typical examples, andtheir modifications and variations are apparent to those skilled in theart. It should be noted that those skilled in the art can make variousmodifications to the above-described embodiments without departing fromthe principle of the invention and the accompanying claims.

What is claimed is:
 1. An apparatus for determining a position of a mobile wireless station, said apparatus comprising: means for determining the position of said mobile wireless station in accordance with a position of a first reference wireless station, a position of a second reference wireless station, a first relative angular direction between said mobile wireless station and said first reference wireless station, and a second relative angular direction between said mobile wireless station and said second reference wireless station.
 2. An apparatus according to claim 1, wherein said first and second relative angular directions are angular directions of said first and second reference wireless stations relative to a reference angular direction of said mobile wireless station.
 3. An apparatus according to claim 1, wherein said first relative angular direction is determined in accordance with a first phase difference associated with a first RF signal from said first reference wireless station which is received by said mobile wireless station, and said second relative angular direction is determined in accordance with a second phase difference associated with a second RF signal from said second reference wireless station which is received by said mobile wireless station.
 4. An apparatus according to claim 1, wherein said first relative angular direction is an angular direction of said mobile wireless station relative to a reference angular direction of said first reference wireless station, and said second relative angular direction is an angular direction of said mobile wireless station relative to a reference angular direction of said second reference wireless station.
 5. An apparatus according to claim 1, wherein the position of said mobile wireless station is determined further in accordance with a third relative angular direction between said first reference wireless station and said second reference wireless station.
 6. An apparatus according to claim 1, wherein said first relative angular direction is determined in accordance with a first phase difference associated with an RF signal from said mobile wireless station which is received by said first reference wireless station, and said second relative angular direction is determined in accordance with a second phase difference associated with an RF signal from said mobile wireless station which is received by said second reference wireless station.
 7. An apparatus according to claim 1, wherein said position determining means determines the position of said mobile wireless station in accordance with the positions of said first and second reference wireless stations, said first and second relative angular directions, a position of a third reference wireless station, and a third relative angular direction between said mobile wireless station and said third reference wireless station.
 8. An apparatus according to claim 7, wherein the position of said mobile wireless station is determined in accordance with at least two of three angles between said first, second and third relative angular directions.
 9. An apparatus according to claim 1, wherein said apparatus is said mobile wireless station.
 10. An apparatus according to claim 1, wherein said apparatus is one of said first and second reference wireless stations.
 11. An apparatus according to claim 1, wherein said apparatus is connected to said first reference wireless station via a local area network.
 12. An apparatus for determining an angular direction of a wireless station, comprising means for determining the angular direction of said wireless station relative to a reference angular direction, in accordance with a phase difference associated with a received RF signal.
 13. An apparatus according to claim 12, wherein said RF signal is received from said wireless station.
 14. An apparatus according to claim 12, wherein said RF signal is received by said wireless station.
 15. An apparatus according to claim 12, wherein said phase difference is a phase difference associated with said received RF signal between two antennas.
 16. An apparatus according to claim 12, wherein said apparatus is said wireless station.
 17. An apparatus according to claim 12, wherein said apparatus receives said RF signal from said wireless station.
 18. An apparatus according to claim 12, wherein said apparatus receives said phase difference.
 19. An apparatus according to claim 12, wherein said apparatus further comprises means for determining a position of said wireless station from the determined angular direction.
 20. A wireless device comprising: first and second antennas displaced from each other by a predetermined distance for receiving an RF signal; and means for detecting a phase difference associated with said received RF signal between said first and second antennas.
 21. A wireless device according to claim 20, further comprising means for detecting source identification included in said received RF signal.
 22. A program stored on a storage medium for an information processing apparatus, said program being operable to effect the steps of: obtaining a first relative angular direction between a mobile wireless station and a first reference wireless station; obtaining a second relative angular direction between said mobile wireless station and a second reference wireless station; and determining a position of said mobile wireless station in accordance with a position of said first reference wireless station, a position of said second reference wireless station, said first relative angular direction, and said second relative angular direction.
 23. A program according to claim 22, being operable to further effect the steps of: determining said first relative angular direction in accordance with a first phase difference associated with a first RF signal from said first reference wireless station which is received by said mobile wireless station, and determining said second relative angular direction in accordance with a second phase difference associated with a second RF signal from said second reference wireless station which is received by said mobile wireless station.
 24. A program according to claim 22, wherein the step of determining a position comprises determining the position of said mobile wireless station further in accordance with a third relative angular direction between said first reference wireless station and said second reference wireless station.
 25. A program according to claim 22, being operable to further effect the steps of: determining said first relative angular direction in accordance with a first phase difference associated with an RF signal from said mobile wireless station which is received by said first reference wireless station, and determining said second relative angular direction in accordance with a second phase difference associated with an RF signal from said mobile wireless station which is received by said second reference wireless station.
 26. A program according to claim 22, wherein the step of determining a position comprises determining the position of said mobile wireless station in accordance with the positions of said first and second reference wireless stations, said first and second relative angular directions, a position of a third reference wireless station, and a third relative angular direction between said mobile wireless station and said third reference wireless station.
 27. A program stored on a storage medium for an information processing apparatus, said program being operable to effect the steps of: obtaining a phase difference associated with a received RF signal; and determining the angular direction of said wireless station relative to a reference angular direction, in accordance with said phase difference.
 28. A program according to claim 27, being operable to further effect the step of determining a position of said wireless station in accordance with the determined angular direction.
 29. A method for determining a position of a mobile wireless station, said method comprising: obtaining a first relative angular direction between said mobile wireless station and a first reference wireless station; obtaining a second relative angular direction between said mobile wireless station and a second reference wireless station; and determining a position of said mobile wireless station in accordance with a position of said first reference wireless station, a position of said second reference wireless station, said first relative angular direction, and said second relative angular direction.
 30. A method according to claim 29, further comprising the steps of: determining said first relative angular direction in accordance with a first phase difference associated with a first RF signal from said first reference wireless station which is received by said mobile wireless station, and determining said second relative angular direction in accordance with a second phase difference associated with a second RF signal from said second reference wireless station which is received by said mobile wireless station.
 31. A method according to claim 29, wherein the step of determining a position comprises determining the position of said mobile wireless station further in accordance with a third relative angular direction between said first reference wireless station and said second reference wireless station.
 32. A method according to claim 29, further comprising the steps of: determining said first relative angular direction in accordance with a first phase difference associated with an RF signal from said mobile wireless station which is received by said first reference wireless station, and determining said second relative angular direction in accordance with a second phase difference associated with an RF signal from said mobile wireless station which is received by said second reference wireless station.
 33. A method according to claim 29, wherein the step of determining a position comprises determining the position of said mobile wireless station in accordance with the positions of said first and second reference wireless stations, said first and second relative angular directions, a position of a third reference wireless station, and a third relative angular direction between said mobile wireless station and said third reference wireless station.
 34. A method for determining an angular direction of a wireless station, said method comprising the steps of: obtaining a phase difference associated with a received RF signal; and determining the angular direction of said wireless station relative to a reference angular direction, in accordance with said phase difference.
 35. A method according to claim 34, further comprising the step of determining a position of said wireless station from the determined angular direction 